Many pressure containing vessels such as pipelines, pressurized tanks and the like are provided with closure devices that provide access thereto. In some cases the pressurized gaseous contents of the pressure vessel can represent a hazard to workers should the contents be vented to the atmosphere. In most cases, the physical properties of pressure vessel closures are such that it is relatively impossible for workers to open the closure while the pressure vessel is maintained under pressure of significantly high value. Where the closure is quite large (as for example, pipelines having 36" diameters), pressure induced forces developed by minimal or nominal pressure conditions can subject workers to physical injury in the event of sudden venting of the closure under pressure.
In many cases closures for pipelines, pressure vessels and the like are of the quick-opening type, thus allowing them to opened by minimal rotation such as a partial or single revolution for low pressure vessels or a minimal number of revolutions for high pressure vessels. In these cases, it is highly desirable that workers be aware of the pressure conditions of the vessel prior to opening the closure. It is therefore desirable to provide a safety device for the closures of pressure containing vessels to thus insure that opening of the closure can be accomplished only when the internal pressure of the vessel is of sufficiently neglible nature that pressure-induced force acting on the closure is at a safe level that workers are not endangered.
In many cases, the product contained within the pressure vessel is of sufficiently hazardous nature to workers in and about the area thereof, it is imperative that the product be prevented from any release into the atmosphere. For example, large gas pipelines may control the flow of sour gas containing high percentages of hydrogen sulfide which is well known to be hazardous to workers. It is desirable therefore to provide a pressure actuated safety device for the closures of pipelines, pressure vessels and the like, wherein workers may manually inspect the internal pressure condition of the pipeline or pressure vessel without releasing any of the hazardous gaseous material into the atmosphere where it might constitute a danger to the workers. Although the present invention is direted primarily to safety for gas handling systems, such is not intended to limit the spirit and scope of the invention. The safety device disclosed herein may also be employed in liquid handling systems as well.
In many cases, closures for various pressure vessels are provided having venting devices to ensure that the vessel contains no pressure prior to opening of the closure. These venting-type safety devices are impractical under circumstances where the product within the pressure vessel constitutes a hazard to workers involved. It is thus desirable to ensure that workers have the capability of efficiently and safely controlling the opening and closing movement of the closures of pressure vessels under circumstances that ensure against the venting of any hazardous constituents into the atmosphere.